In 1992, KBKhA Kosberg began the development of a new hydrogen-oxygen rocket engine, to feature a novel expansion-deflection nozzle.
[1] In this arrangement, the combustion chamber of the engine is placed downstream of the nozzle throat, where the flow of exhaust gases is supersonic.
In 1995, KBKhA, using internal funding, continued to develop the engine for roles such as launch vehicle upper stages and space tugs.
The testing confirmed the predicted properties of the engine and showed that flow separation did not occur within the nozzle when the non-regeneratively cooled extension was not installed.
The engine was planned to form the basis of the upper stage of the now-cancelled Onega launch vehicle, a major upgrade to the Soyuz-2.1.